Cu掺杂量对Zn-Cu共掺TiO2薄膜光学带隙的影响

采用溶胶-凝胶旋涂法,分别以钛酸四丁酯(Ti(O C₄H₉)₄)为钛源、硝酸锌(Zn(NO₃)₂·6H₂O)为锌源、硝酸铜(Cu(NO₃)₂·3H₂O)为铜源制备了不同掺杂量的Zn、Cu共掺TiO₂薄膜。分别采用X射线衍射仪(XRD )、薄膜测厚仪、紫外-可见分光光度计(UV-Vis)对所制备的样品进行表征。结果表明 :与本征TiO₂和2.0 at%Zn²⁺-TiO₂相比,Cu²⁺的掺 杂减小了样品的晶面间距及晶粒尺寸、增加了样品的半高宽及比表面积,进而提高了薄膜的 光催化活性能。随着Cu²⁺掺杂量的增加,样品沿(101)晶面择优取向先增强后减弱 ,薄膜的吸光度呈现先升高后降低的趋势,TiO₂的 带隙值由3.424 eV减小到3.325 eV。与本征TiO₂和2.0 at%Zn²⁺-TiO₂相比 ,2.0at%Zn²⁺－1.0 at%Cu²⁺-Ti O₂的样品结晶度最好,(101)晶面择优取向最佳,薄膜表面的缺陷较少、较为均匀平整 且吸光度更好,光学带隙值最小为3.325 eV。     

SO2-4/Bi2O3固体超酸的制备及其可见光催化性能

采用水热法结合H2SO4浸泡处理成功合成了SO^2-₄/Bi₂O₃可见光催化材料, 并采用XRD、TG DTA和UV Vis等对合成产物的物相结构、热化学性能、光吸收性能以及可见光催化性能进行了研究, 对H2SO4浸泡工艺条件对产物的可见光催化性能的影响进行了探讨。研究表明, 水热合成产物为α-Bi₂O₃、Bi₂O₄和Bi₂O₂CO₃的混合物, 其中α-Bi₂O₃为主要成分;H₂SO₄浸泡处理并未改变产物的物相结构, 但经H₂SO₄浸泡处理后产物的光催化性能得到了显著的提高, 并且H₂SO₄浸泡工艺条件对产物的光催化活性有着重要的影响。在实验范围内, 在浓度为0.5mol·L^-1的H₂SO₄溶液中浸泡75min, 再经700℃热处理4h可制备出具有较佳光催化活性的产物, 经75min可见光的照射后对甲基橙溶液的光催化脱色率可达93.1%。     

溅射压强对ITO/Cu2O复合膜结构和光学性能的影响

利用脉冲磁控溅射制备技术,以氧化铟锡(ITO)导电玻璃为基底,采用单质金属Cu 靶作为溅射靶,在O₂和Ar的混合气氛下沉积了Cu₂O薄膜。通过调控溅射压强,研 究了脉冲磁控溅射沉积法在不同溅 射压强下对Cu₂O薄膜的物相结构、表面形貌及光学性能的影响。结果表明,在O₂、Ar流 量比(O₂/Ar)为20∶90的气 氛条件下,在2～3Pa的溅射压强范围内,可获得纯相的Cu₂O薄膜;薄膜表面形貌依赖于 溅射压强,薄膜表面粗糙度的 均方根(RMS)值随溅射压强的增大而减小;在ITO上沉积Cu₂O 薄膜后,薄膜的光学吸收边红移至780 nm, ITO/Cu₂O复合膜的光谱吸收范围拓展至300～780 nm,复合膜的吸收强度随溅射压强的增 大而减小,光学带隙E_g 随溅射压强的增大而增大,E_g值为2.28～2.39eV。     

Co3O4/Fe2O3异质结复合材料的制备及其紫外光光电探测性能

分别采用旋涂法和水热法在FTO衬底上制备Co₃O₄种子层和Co₃O₄薄膜,再在Co₃O₄薄膜上水热生长Fe₂O₃纳米棒,获得了高质量的Co₃O₄/Fe₂O₃异质结复合材料。通过改变Fe₂O₃前驱体溶液浓度来改变异质结复合材料中Fe₂O₃组分的含量。结果表明,Fe₂O₃纳米棒覆盖在呈网状结构的Co₃O₄薄膜上,随着Fe₂O₃前驱体溶液浓度即Fe₂O₃组分含量的增加,Co₃O₄/Fe₂O₃异质结复合材料对紫外光的响应逐渐增强,当Fe₂O₃前驱体溶液浓度为0.015mol/L时,异质结复合材料有着很好的光电稳定性,并表现出较高的响应率(12.5mA/W)和探测率(4.4×10¹⁰Jones)。     

CaBi2Ta2O9基压电陶瓷改性研究

该文采用传统固态反应法制备了Ca_1-x(Li_0.5Ce_0.4Pr_0.1)_xBi₂Ta₂O₉(x为摩尔分数)陶瓷,研究了(Li_0.5Ce_0.4Pr_0.1)²⁺复合离子不同掺杂浓度对陶瓷结构和电学性质的影响。结果表明,在选定浓度范围内,(Li_0.5Ce_0.4Pr_0.1)²⁺复合离子改善了CaBi₂Ta₂O₉基陶瓷的压电活性与高温下的直流电阻等特性。当x=0.08时,陶瓷具有最佳综合性能,即压电常数d₃₃=10.3 pC/N,居里温度TC=928 ℃,直流电阻率ρ=1.12×10⁶ Ω·cm(650 ℃),介电损耗tan δ=0.026(1 MHz,650 ℃)。     

退火Cu2O薄膜的结构及光学特性

采用射频(RF)磁控溅射单质金属铜(Cu)靶, 在O₂和Ar的混合气氛下制备了Cu₂O薄 膜,并在N₂气氛下对预沉积的Cu₂O薄膜进行快速光热退火(RTA)处理,研究了 衬底温度及退火温度对Cu₂O 薄膜的生长行为、物相结构、表面形貌及光学性能的影响。结果表明,衬底温度在300℃以 下预沉积的Cu₂O薄膜 为非晶薄膜,退火处理对Cu₂O薄膜的结晶行为有明显影响,在N₂气氛下对Cu₂O薄膜进 行退火处理不影响薄膜的物 相结构;预沉积和退火Cu₂O薄膜在650nm以下波长范围内均有较强 吸收,吸收强度随退火温度的增加而增强,薄 膜在400nm以下波长范围内出现两个由缺陷引起的中间带(IB)吸收行 为,快速热退火处理不能减少或消除薄膜沉积 过程中形成的缺陷态;退火处理影响薄膜的光学带隙Eg,预沉 积薄膜经600℃退火处理,E_g值增大了 0.26eV。     

Ca3Y2(Si3O9)2:Tb3+绿色荧光粉的光谱特性

采用高温固相法制备了Ca₃Y₂(Si₃O₉)₂: Tb³⁺绿色荧光粉,研究了材料的光学性能。X 射线衍射(XRD)结果显示,掺杂少量的Tb³⁺,并未影响Ca₃Y₂(Si₃O₉)₂材料 的晶相结构。Ca₃Y₂(Si₃O₉)₂:Tb³⁺ 荧光粉的激发光谱由较强的4f^75d1宽带吸收(200～300 nm )和较弱的4f-4f电子跃迁吸收 (300～500 nm)构成,主激发峰位于236nm。取波长分别为236、376和482nm的光 作为激发源时,发现样品的主发射峰均位于544 nm,对应Tb³⁺的⁵D 4→⁷F₅跃迁发射。以236nm 紫外光作为激发源,监测544nm主发射峰,随Tb³⁺浓度 的增大,Ca₃Y₂(Si ₃O₉)₂:Tb³⁺的荧光寿命逐渐减小,但在实验范围内并未出现浓度猝灭现象。     

TiO2基染料敏化太阳能电池的表面修饰及性能研究

采用水热法制备TiO₂浆料,用La(NO₃)₃溶 液浸泡TiO₂薄膜获得修饰电极。用X射线光电子能谱(XPS) 和扫描电子显微镜(SEM)对修饰电极的主要成分及形貌进行表征的结果显示,电极薄膜分为 上下两层,表 面包覆层粒径较大,为La₂O₃颗粒;下层颗粒粒径较小,为TiO₂颗粒。电流-电压测 试结果显示,与修饰 前相比,用La(NO₃)₃溶液浸泡30min获得的膜电极性能最优,使 开路电压和短路电流分别提高了6.8%和 18.5%。电化学阻抗谱(EIS)测试结果表明,相同偏压下,TiO₂/La ₂O₃电极界面复合电阻比TiO₂要大,说明 La₂O₃包覆层在一定程度上抑制了界面的电子复合,改善了电池的光电化学性能。     

Gd2O3:Yb3+,Er3+纳米粉体的水热合成及上转换发光研究

采用Gd₂O₃,Yb₂O₃,Er₂O₃,HNO₃,CO(NH₂)₂和C ₁₂H₂₅SO₄Na为实验原料,通过水热法合成了纳米Gd₂O₃:Yb³⁺,Er ³⁺上转换发光粉体。通过X射线衍射(XRD )、差示扫描量热 -热重分析(DSC-TGA )、傅里叶变换红外光谱(FT-IR ) 、透射电子显微镜(TEM )和 上转换发射光谱(UCL )等对样品进行表征。研究结果表明:CO(NH₂)₂与Gd ³⁺ 离子的摩尔比m影响前驱体的组成,当m=4时,前驱体是由晶态的 Gd₂(CO₃)₃·xH₂O构成。该 前驱体在空气气氛下800℃煅烧2h可获得单相的Gd₂O₃纳米粉体 ,粉体呈近球状,平均粒 径约为30～40nm。上转换发光光谱表明,在980nm波长红外光激发下,Gd₂O₃:Yb³⁺,Er³⁺的主发射峰 位于664nm波长处,呈红光发射,对应于Er³⁺的 ⁴F9/2→⁴I15/2跃迁。在波长为539 nm和562nm附近呈现绿光发射,分别对应于Er³⁺的²H11/2→⁴I15/2和⁴S3/2→⁴I15/2跃迁。Er³⁺的猝 灭浓度为1%。800℃煅烧合成的Gd₂O₃:Yb³⁺,Er³⁺ 纳米粉体的上转换发光机制为双光子模型, 而1200℃煅烧合成的Gd₂O₃:Yb³⁺,E r³⁺纳米粉体的上转换发光机制则为三光子模型。     

Mn0.1Ti0.9O2-δ稀磁半导体薄膜的MBE生长及表征

采用OPA-MBE方法在SrTiO3(STO)衬底上成功制备了Mn_0.1Ti_0.9O_2-δ(MTO）稀磁半导体薄膜. 利用X射线衍射仪、X射线光电子能谱仪、紫外可见光分度计以及直流四探针测试仪研究了薄膜的晶体结构、化学组成、光吸收和电荷输运性质. MTO薄膜具有锐钛矿和金红石的混合相，光吸收带边界发生“红移”，电荷输运性质明显提高，室温环境下电阻率仅为37.5Ω·m.     

Effects of excess Bi concentration, buffered Bi2O3 layer, and Ta doping on the orientation and ferroelectricity of chemical-solution-deposited Bi3.25La0.75Ti3O12 films

Effects of excess Bi concentration, buffered Bi₂O₃ layer, and Ta doping on the orientation and ferroelectricity of chemical-solution-deposited (CSD) Bi_3.25La_0.75Ti₃O₁₂ (BLT) films on Pt/SiO₂/Si(100) were studied. The optimum concentration of excess Bi added to the BLT films to achieve a larger remanent polarization (2Pr) was 10 mol.%. The buffered Bi₂O₃ layers could reduce the temperature for c-axis-oriented growth of BLT films from 850°C to 700°C. However, two-step annealing, i.e., first annealed at 650°C and then annealed at a temperature of 700–850°C, could effectively suppress the c-axis-oriented growth and thus improve the 2Pr of BLT films. The improvement of the 2Pr of BLT films can be explained in terms of the large polarization along the a-axis orientation and buffered Bi₂O₃ layers, which compensate the BLT films for Bi evaporation during annealing. The Ta doping can induce two contrary effects on the 2Pr of BLT films. For the (Bi_3.25La_0.75)(Ti_3−xTa_x)O₁₂ (BLTTx) films with x=0.005, the effect of a decrease of oxygen vacancies would be dominant, resulting in the improvement of 2Pr. Because the Ta concentration (x) in the BLTTx films exceeds 0.01, the effect of a decrease of grain size would become dominant, resulting in the degradation of 2Pr.     

Preparation and characterization of thin films of MgO,Al2O3 and MgAl2O4 by atomic layer deposition

MgO, Al₂O₃ and MgAl₂O₄ thin films were deposited on silicon substrates at various temperatures by the atomic layer deposition (ALD) method using bis(cyclopentadienyl)magnesium, triethylaluminum, and H₂O and were characterized systematically. High-quality polycrystalline MgO films were deposited for a substrate temperature above 500°C, and amorphous thin films were deposited around 400°C. The deposited Al₂O₃ and MgAl₂O₄ thin films were characterized as amorphous in structure. Applicability of ALD to complex oxides is discussed.     

Infrared spectroscopy and X-ray diffraction studies on the crystallographic evolution of La2O3 films upon annealing

Rare earth oxides (REOs) have lately received extensive attention in relation to the continuous scaling down of non-volatile memories (NVMs). In particular, La₂O₃ films are promising for integration into future NVMs because they are expected to crystallize above 400 °C in the hexagonal phase (h-La₂O₃) which has a higher κ value than the cubic phase (c-La₂O₃) in which most of REOs crystallize. In this work, La₂O₃ films are grown on Si by atomic layer deposition using La(C₅H₅)₃ and H₂O. Within the framework of the h-La₂O₃ formation, we systematically study the crystallographic evolution of La₂O₃ films versus annealing temperature (200-600 °C) by Fourier transform infrared spectroscopy (FTIR) and grazing incidence X-ray diffraction (GIXRD). As-grown films are chemically unstable in air since a rapid transformation into monoclinic LaO(OH) and hexagonal La(OH)₃ occurs. Vacuum annealing of sufficiently thick (>100 nm) La(OH)₃ layers induces clear changes in FTIR and GIXRD spectra: c-La₂O₃ gradually forms in the 300-500 °C range while annealing at 600 °C generates h-La₂O₃ which exhibits, as inferred from our electrical data, a desirable κ ∼ 27. A quick transformation from h-La₂O₃ into La(OH)₃ occurs due to H₂O absorption, indicating that the annealed films are chemically unstable. This study extends our recent work on the h-La₂O₃ formation.     

Microwave properties of epitaxial large-area Ca-doped YBa2Cu3O7−δ thin films on r-plane sapphire

Ca doping of YBa₂Cu₃O_7−δ (YBCO) is well known to enhance the critical current density in large-angle grain boundaries for example of bicrystals. However, up to now no data are available on microwave properties of epitaxial Ca-doped YBa₂Cu₃O_7−δ thin films on r-plane sapphire with CeO₂ buffer layer.Therefore, first results are presented for large-area pulsed laser deposition (PLD) grown Ca_xY_1−xBa₂Cu₃O_7−δ films on 3-in. diameter sapphire wafers. The PLD process is optimised for undoped YBCO thin films and shows high reproducibility for YBCO. The microwave surface resistance R_s at 8.5 GHz of Ca-doped YBCO (x=0.1) thin films shows clear reduction (up to 20%) with respect to that of YBCO for temperatures from about 20–50 K. In addition, microwave surface resistance R_s of Ca-doped YBCO is lower than that of YBCO even for enhanced microwave surface magnetic field up to about 20 mT for temperatures 20 and 40 K.     

Etch damage evaluation on (Bi4−xLax)Ti3O12 thin films during the etch process using inductively coupled plasma sources

The etching mechanism of (Bi_4−xLa_x)Ti₃O₁₂ (BLT) thin films in Ar/Cl₂ inductively coupled plasma (ICP) and plasma-induced damages at the etched surfaces were investigated as a function of gas-mixing ratios. The maximum etch rate of BLT thin films was 50.8 nm/min of 80% Ar/20% Cl₂. From various experimental data, amorphous phases on the etched surface existed on both chemically and physically etched films, but the amorphous phase was thicker after the 80% Ar/20% Cl₂ process. Moreover, crystalline “breaking” appeared during the etching in Cl₂-containing plasma. Also the remnant polarization and fatigue resistances decreased more for the 80% Ar/20% Cl₂ etch than for pure Ar plasma etch.     

Study on the multiferroic properties of 2-2 type of BiFeO3-CuFe2O4 thin films

The 2-2 type BiFeO₃-CuFe₂O₄(BFO-CFO) bilayer thin films were deposited on FTO/glass substrates by sol-gel method, using Bi(NO₃)₃·5H₂O, Fe(NO₃)₃·9H₂O and Cu(NO₃)₃·3H₂O as the raw materials. The structure, surface morphologies and electric properties of the thin films were investigated. The XRD patterns show that the structure of BFO is the distorted rhombohedral perovskite with R3c:H (161) space lattice, CFO is the tetragonal spinel with type I41/amd (141) space lattice. The interface is obvious between the CFO and BFO films, which shows that the BFO and CFO have no inter-diffusion phenomena. When the frequency is 10 kHz, the dielectric loss peak is consistent with the dielectric relaxation of Wagner Maxwell. The leakage current density of BFO-CFO under positive and negative bias voltages is asymmetric, and there is a hysteresis phenomenon in the positive bias voltage. The results of XPS show that the Fe²⁺ of the BFO-CFO is decreased and the leakage current of the film is improved. The saturation magnetization (M_s) of BFO-CFO is 25.8 emu/cm³ at room temperature, which is about 40 times of the pure BFO.     

In-situ monitoring of the growth of Bi2 Te2 and Sb2 Te3 films and Bi2 Te3-Sb2 Te3 superlattice using spectroscopic ellipsometry

In this work, we present in-situ monitoring of the growth of bismuth telluride (Bi₂Te₃) and antimony telluride (Sb₂Te₃) thin films as well as Bi₂ Te₃-Sb₂Te₃ superlattice using a spectroscopic ellipsometer (SE). Bi₂Te₃ and Sb₂ Te₃ films were grown by metalorganic chemical vapor deposition (MOCVD) at 350 C. A44-wavelength ellipsometer with spectral range from 404 nm to 740 nm was used in this work. The optical constants of Bi₂ Te₃ and Sb₂Te₃ at growth temperature were determined by fitting a model to the extracted in-situ SE data of optically thick Bi₂ Te₃ and Sb₂ Te₃ films. Compared to the optical constants of Bi₂ Te₃ and Sb₂ Te₃ at room temperature, significant temperature dependence was observed. Using their optical constants at growth temperature, the in-situ growth of Bi₂ Te₃ and Sb₂ Te₃ thin films were modeled and excellent fit between the experimental data and data generated from the best-fit model was obtained. In-situ growth of different Bi₂ Te₃-Sb₂ Te₃ superlattices was also monitored and modeled. The growth of Bi₂ Te₃ and Sb₂ Te₃ layers can be seen clearly in in-situ SE data. Modeling of in-situ superlattice growth shows perfect superlattice growth with an abrupt interface between the two constituent films.     

The Effect of Cu Addition on the System Stability and Thermoelectric Properties of Bi2Te3

Cu-doped Bi₂Te₃ nanopowders with nominal composition Cu _x Bi₂Te₃ (x = 0, 0.01, 0.025, and 0.05) were synthesized by a gas-induced-reduction method using TeO₂, Bi(NO₃)₃·5H₂O and Cu(NO₃)₂·3H₂O as raw materials and then hot-pressed into bulk materials. x-Ray diffraction (XRD) analysis indicates that, when x ≠ 0, pure Cu _x Bi₂Te₃ phase was obtained, and that when x = 0, Bi₂Te₃ mixed with a small amount of Bi₂TeO₅ was obtained. Field emission scanning electron microscopy observation reveals that Cu addition significantly reduces the grain sizes of the materials. First-principle calculations show that the order of the free energies of the materials is: Cu-doped Bi₂Te₃ (substitution of Cu for Bi) < Cu intercalated Bi₂Te₃ < Bi₂Te₃. The electrical and thermal conductivities decrease and the Seebeck coefficient increases with Cu addition. The maximum figure of merit, ZT, reaches 0.67 at 500 K for a Cu_0.05Bi₂Te₃ sample.     

YBa2Cu3-xZnxO7薄膜红外探测器的研究

在对红外探测器进行理论分析的基础上,设计并研制了液氮温度下的Yba2Cu3-xZnxO7薄膜红外探测器,系统地测试了器件的特征参数.最好的结果为:对于波长为10μm,调制频率为f=500Hz,带宽为Δf=1Hz的红外输入辐射Rv(500,10,1)=3587V/W,NEP(500,10,1)=6.5×10-12W/Hz1/2,D*(500,10,1)=7.2×1012cmHz1/2/W,τ(500,10,1)=1.2ms.     

Characterization and ellipsometric investigation of high-quality ZnO and ZnO(Ga2O3) thin alloys by reactive electron-beam co-evaporation technique

High-quality ZnO(Ga₂O₃) thin films have been co-evaporated by reactive electron-beam evaporation in an oxygen environment. The effect of Ga₂O₃ on the structural and optical properties has been investigated. X-ray diffraction (XRD) measurements have shown that the ZnO(Ga₂O₃) alloys are c-axis-oriented. The alloy containing 28% of Ga₂O₃ showed the best crystallinity. Photoluminescence on ZnO(28%Ga₂O₃) reveals an enhancement of the ultraviolet near band edge emission at 380 nm while the intensity of the deep-level emissions weakens. A reduction of the oxygen vacancies as well as the reduction of the zinc interstitials with gallium may explain this effect. Thus, the possibility of transitions of electron in the conduction band to a deep acceptor level due to zinc interstitials may decrease. Finally, ellipsometric measurements show that the optimum weight concentration of gallium oxide in the alloys is 28%, thus correlating with the XRD and photoluminescence measurements.